How big are these lists? If they're not incredibly large, something like this should work:

# Assuming @list_a and @list_b

my %b;
$b{$_} = 1 foreach (@list_b);

my @list_c;
foreach (@list_a) {
    push @list_c, $_ unless $b{$_};
}

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In reply to Re: comparing lists and getting an exemtion report by Riales
in thread comparing lists and getting an exemtion report by Saadat.123

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